A consortium of investigators at Brown University in the Division of Biology & Medicine and the Departments of Physics, Chemistry, and Engineering is requesting support from the NCRR Shared Instrumentation Grant for purchase of a JASCO J-810 CD spectropolarimeter. At Brown CD is used to analyze a broad range of samples that include peptides, proteins, nucleic acids, and their complexes, providing unique information on structure, stability, and dynamics, including thermodynamic and kinetic parameters of these systems. The deteriorating performance (e.g., poor UV, below 200 nm, penetration) of the current CD instrument (approaching its 15th year in operation) places severe limitations on the scientific problems that can be undertaken. The requested instrument with computer controlled temperature variation, a syringe-based titration and stop-flow system, and simultaneous CD and fluorescence absorption will allow for a large number of experiments currently not possible. These include thermo-melting curves for stability determination, .accurate titrations of solvents, buffers, denaturants, ligands, or binding partners and the temporal determination of the structural variation induced by alteration of these variables. We will be able to correlate structural changes (CD) with binding events (e.g., as monitored by changes in tryptophan or use of fluorescent ligands) by the simultaneous acquisition of CD and fluorescence absorption. As detailed in this proposal, such studies are (or will become) an integral part of a number of NIH sponsored research projects and therefore the instrument will have an immediate and long-lasting impact on the biomedical research conducted at Brown University. [unreadable] [unreadable]